The present invention relates to portable hand-held devices for extracted blood elements, such as blood plasma, from whole blood.
The use of blood sampling devices is known in the art. Typically, blood samples are taken from a patient utilizing a finger stick or draw tube. As is recognized in the art, the obtained sample is difficult to analyze. For example, the sample contains a variable proportion of cells which affect the quantization of analytes measured in non-equilibrium assays. The blood sample is subject to clotting with the end result of clogging the small channels in typical blood analyzers. The blood sample contains fragile blood cells that, if ruptured, can alter the concentration of some analytes. Moreover, a very high number of blood cells could overwhelm the read capability of an analyzer that is cytometer-based. Some sampling devices known in the art, such as, for example, described in U.S. Pat. No. 5,919,356, utilize a needle that is insertable into a patient to draw blood, by pulling a plunger of a syringe, which then flows into a chamber that contains membrane fibers. Filtration through the membrane is accomplished by either shaking the device or by depressing the plunger of the syringe. The separated sample is contained in a collector chamber. Devices of this type are not intended for use with a blood analyzer. Moreover, the devices of the prior art, such as described above, require puncturing the skin of a patient by way of a needle/syringe arrangement to extract an unnecessarily large volume of blood from the patient. This presents a potential trauma affect on patients sensitive to needle punctures of their skin. The present invention serves to remedy the shortcomings of the prior art.
The present invention is directed to a device for collecting a blood sample that is to be analyzed by the use of a blood analyzer. The device comprises a hollow fluid tight tube having an inlet opening for receiving a blood sample and a separation filter in the tube that serves to separate out desired blood constituents for later analysis. Such a constituent is blood plasma and the filter is hollow and contains a plurality of pores sized to prevent whole blood and blood cells from passage into the hollow part of the filter while providing passage of blood plasma through the filter. The tube has a wettable surface and the relative size of the filter within the tube provides for self-filling capability of the device through capillary action, thus providing self-filling capability combined with a blood separation filter in one device. The device includes a conduit that extends from the filter to the outlet of the device. The conduit is a stent-like structure that has a tapered end for easy penetration into a septum of an analyzer that acts as a self-closing sample inlet channel in the analyzer manifold. Annularly disposed about the outlet of the device is a shield that extends away from the outlet a distance greater than the separated blood conduit. The shield protects the conduit from inadvertent contact by the user of the device. This protects the sample from any contamination by a user and prevents the user from contact with a contaminated sample.
In practice, a droplet of blood is introduced at the device inlet and by virtue of the combined affects of the wettable interior surface of the tube and the interior fill volume, blood is drawn into the device under capillary action into the device. The device is placed on an analyzer such that the separated blood conduit pierces the inlet channel septum whereupon a vacuum is drawn by the analyzer to draw the blood sample through separation filter thereby introducing the separated blood, i.e., blood plasma, into the analyzer.
As an alternate embodiment of the present invention, the inlet of the device may be formed with a sharp projection to act as a blood drawing lancet and the shield may be in the form of an anchoring device, such as a Luer Lock. As a result of the aforementioned features, the present invention is characterized as being a point of need clinical analyzer; that is compact and portable; that provides a small volume of plasma in a relatively short period of time; that is relatively inexpensive compared to traditional blood draw disposables; that protects the operator from contact with potentially infectious sample; and lastly does not require a dedicated piece of equipment to separate plasma from cells.